2 Answers
2

Long Answer: When you have delegate calendars, that typically means that you are given permission to view (maybe edit) someone else's calendar. This is why there is special interface to deal with delegation and they are grouped in their own section of the calendar list.

Behind the scenes, google treats each calendar you create as its own principal (almost like its own account), so iCal treats all the non default calendars as delegates. To confuse things further, you can actually can share google calendars so iCal could never tell the difference between an actual shared calendar and new calendar you added.

The only solution is to move all your events into the default calendar or move your calendars to a service which handles multiple calendars in a better way (Yahoo, Exchange, iCalServer)